This invention relates to valves and, more particularly, to pilot-operated inflation valves that control a pressure medium manually, electrically and/or pneumatically.
Inflation devices or pontoons can be used on aircraft, such as helicopters, to permit them to land on water. An inflated pontoon, however, is rather bulky and diminishes the performance of the aircraft. Therefore, various means have been provided in the prior art for inflating these pontoons when a landing is expected and then retracting them during normal flight. Examples of these are contained in U.S. Pat. No. 3,004,737 to Boyle, et al. and U.S. Pat. No. 3,102,705 to Namsick.
Typically, the pontoons are inflated by a pump or compressed gas supply under the control of a valve. This valve is operated electrically by the pilot of the aircraft. In order to improve the safety of the aircraft when such a pontoon is in use, it is not unusual for these valves to be manually operable so that a safe landing can still be made in the event of an electrical failure.
An electrically-operated valve that might be used for pontoon inflation is described in U.S. Pat. No. 4,180,241 to Fiedler. The Fiedler valve will also operate when presented with a pressure differential that exceeds a preset level. The Fiedler valve additionally provides a manual reset of the valve when an over pressure causes the pneumatic system to operate the valve.
Prior pontoon inflation systems may cause a pilot to make a landing on water when the pontoons are not properly inflated. This can happen when the pontoons are inflated to a pressure less than that required to support the weight of the aircraft. In a case where a single supply of fluid medium is used to inflate pontoons on the left and right side of the aircraft, premature closure of the valve may result in only partial inflation. Visually the pontoons may seem to be fully inflated when they are not. Thus, upon landing the aircraft may sink into the water. The same situation can occur when several tanks are provided for each pontoon. If the valve for only one of the tanks, or less than all of the tanks, opens in response to the signal from the pilot, a partial inflation will occur, but sufficient pressure will not be available.
In a situation in which separate valves extend from a single tank to pontoons on both sides of the aircraft, the operation of only one of these valves will cause one pontoon to inflate and the other to remain uninflated. A quick visual check of the pontoon on the pilot side of the aircraft may show it to be inflated, even though the pontoon on the other side is not. Thus, upon landing in this state, the aircraft will sink into the water on the side without an inflated pontoon.
Because of the critical role that the inflation of pontoons play in the safety of an aircraft, it is important that the inflation valves be operated not only electrically and manually, but also automatically in a manner such that both pontoons are inflated and that the inflation valves remain open until the full supply of pressure medium is delivered to the pontoons.